Genomic and Functional Insights Into Bacillus cereus SH‐10 for Mitigating Lead Stress in Soybean

Beneficial microbes serve as powerful biological tools for enhancing stress tolerance in crops. This study aimed to isolate stress-tolerant, plant growth-promoting bacterium, characterise it using high-throughput next-generation sequencing and expression profiling and assess its potential in improving soybean (Glycine max (L.) Merr.) growth and development under lead (Pb) stress. We identified Bacillus cereus SH-10 as a metal-resistant rhizobacterium capable of tolerating Pb concentrations exceeding 75 mg/kg. When inoculated into soybean plants under Pb stress, SH-10 significantly improved phosphorus and calcium uptake and reduced Pb accumulation. This reduction was associated with increased expression of the stress signalling protein GmCYP82A3. SH-10 also modulated the phytohormone balance by lowering abscisic acid (ABA) levels in shoots and enhancing salicylic acid (SA) biosynthesis. These hormonal shifts corresponded with the downregulation of ABA biosynthesis-related genes (GmNCED1, NCED3, GmbZIP) and the upregulation of the SA biosynthesis gene GmPAL1. Furthermore, SH-10 significantly mitigated oxidative stress in Pb-exposed plants, while enhancing antioxidant activities. The study also identified two phytohormone biosynthesis pathways in rhizobacteria: (1) Terpenes → β-carotene → Xanthoxin → ABA, and (2) Terpenes → Geranylgeranyl diphosphate → gibberellic acid. These findings highlight Bacillus cereus SH-10 as a promising biofertiliser that alleviates Pb toxicity in crops.